Looking Up: Look for the big 'M' of Cassiopeia

Friday

Oct 29, 2010 at 12:01 AMOct 29, 2010 at 9:50 PM

The five most prominent stars of Cassiopeia are wonderfully placed like a prominent letter “W” or “M,” depending on its orientation when you are looking. As Cassiopeia makes its daily spin about the North Celestial pole - the point right by the North Star around which the whole shebang over our heads seems to revolve - the “M” becomes a “W” 12 hours later, and vice-versa. Of course at certain positions the “M” or “W” seems to be standing on one side.

Peter Becker

Last week we emphasized in our column the northern sky constellation Cepheus the King. Mention was made of his mythological wife, Queen Cassiopeia, enshrined forever in our northern sky, right at his side. Cassiopeia has to be one of the most easily recognized and well-known star groups in the sky. The Big Dipper is likely first, and in second place is maybe Orion or Cassiopeia.

The five most prominent stars of Cassiopeia are wonderfully placed like a prominent letter “W” or “M,” depending on its orientation when you are looking. As Cassiopeia makes its daily spin about the North Celestial pole - the point right by the North Star around which the whole shebang over our heads seems to revolve - the “M” becomes a “W” 12 hours later, and vice-versa. Of course at certain positions the “M” or “W” seems to be standing on one side.

On mid-autumn evenings, the “M” shape reaches the point where it is oriented correctly, high up in the northern sky.

Greek astronomer Ptolmey listed Cassiopeia among 48 constellations in the second century. Some view the outline of the constellation as a chair, or throne, upon which the Queen sits.

The Queen is not without her gems. There are numerous interesting stars and star clusters within the borders. Actually, what star ISN’T interesting?

First, here’s two you WON’T see!

One notable star you won’t see was for a while the brightest star in the night sky, and was spotted in Cassiopeia. This was a supernova - a star that literally explodes with such luminance it outshines every star in the galaxy and could be seen from other galaxies in the cosmic neighborhood. (We can easily see supernovae in other nearby galaxies through a telescope.)

The supernova blew in the year 1572 and is known as “Tycho’s Star,” as it was carefully monitored and chronicled by the famed Danish Astronomer Tycho Brahe. It was first seen on Nov. 11, and it briefly was bright enough to be seen in broad daylight. Tycho’s Star gradually faded but was seen by the unaided eye for 16 months.

Another especially interesting star you won’t see in Cassiopeia is the sun! What? Yes, the sun - but you have to be looking from the direction of Alpha Centauri, the closest star system to our sun. Alpha Centauri is exactly opposite in the sky from Cassiopeia and is thus found in the far southern sky, best seen below our equator (it actually is visible as far north as mid-Florida, close to the southern horizon). From Alpha Centauri the sun would appear as a bright yellowish star, magnitude 0.5, the brightest star in Cassiopeia (if that’s what the Alpha Centaurians call it).

How about stars you WILL see?

Two of the fainter stars visible to unaided eyes are among the most luminous stars known.

Magnitude +4.5 Rho Cassiopeiae gives out 550,000 times as much light as the sun. It is a rare yellow “hyper giant,” among only seven of this type known. Another of the seven is also in Cassiopeia, +5th magnitude V509 Cassiopeia.

The Milky Way Band passes through Cassiopeia, providing a rich background of dim stars and star clusters waiting your search with binoculars or telescope. M52 and M103 are two large open clusters here.

The brightest star in the “W” is known as Shedir, or Alpha Cassiopeia. Close by is the famous Double Cluster, actually within the neighboring constellation Perseus. Seen with unaided eyes on a dark night as a double “smudge,” the clusters resolve into two dense patches of fine stars in binoculars.